Do underdrive pulleys kill your alternator/water pump etc...

[HEMISFEAR]

Eventually? I'm wondering if underdrive pulleys put a hurt on other components. Anyone have experience with any adverse effects of using one?

[Vinnysrt8]

I dont think so.

[paxton]

I obviously don't know, but I thought we touched base on this in a discussion with GRRR8on another thread of his. I'll still get the 85MM TB before I ever think of doing the pulleys.

[Red02WS6]

Ive been running an UD pulley for 20k miles and nothing's happend from it, so I would have to say that it doesn't hurt anything. I'm also driving a GM. I'm not sure if there's a difference or not? If there is, I'm assuming not that big of a difference so I think you're safe.

[DevssrT]

I dont think any of the pulleys have been around long enough to see any long term harmful issues occur.

[HEMISFEAR]

I dont think any of the pulleys have been around long enough to see any long term harmful issues occur.

I would tend to agree Ry. Seems like I remember the Mustang guys complaining about having to change alternators like their underwear (once or twice a year) and then it was water pumps that were a big complaint as well. There was a guy on the SRT8OC complaining about his experience with UD pullies and said he'd never run one on his Charger because he learned his lesson with other cars. Could just be because they were Mustangs...IDK lol.

[Jeep Trick]

Mines been fine for about 4000 miles or so, no adverse affects

[BBA]

How can something that drives the accessories slower cause them to fail before they otherwise would have?

I think the cause of people with problems after installing UD pulleys is more likely the person who installed them rather than from what effects the pulleys have. I am sure this get's into overtightening belt issues, overtorque of fasteners when reassembled, etc...

[sound&security]

THE ONLY THING IT HURTS IS THE ALERNATOR not being able to keep up with maintaining THE BATTERYS charge level AND yes ON A MUSTANG OR any ford it burns up the brushes in the alternator. ITS not a good idea to run these on a street car and the lx platform is a big NO-NO unless your ride is a full on track car. the under drive pulleys do just that. They under the alternator and power sterring to free up drag BUT at a cost to the chargeing system. THE lx PLATFORMS HAVE 5 computers runing the car and at a idol the charging system isnt runing fast enuff to keep up with the draw of current used by the tcm/pcm/ecu/abs/hal/ac/lights so your amps and voltage drops and the alternator isnt spining fast enuff to replace the charge that the electronics are sucks dowm off the battery. INTURN you lose electronic throttle responce/low voltage to your coil pac and end up will a weak spark/and the pcm and tcm have trouble in working out the information with weak voltage. THIS is a proven fact. THE ELECTRIC SYSTEM is the heart of the car AND me being a ASE and MECP tech CAN SAY THAT THE MONEY YOU SPEND on a under drive set up isnt worth more than 5 hp on the top end at WOT and the battery you will be going threw and the lost throttle respounce down low and the AC system not blowing as cold isnt worth it. I had a mustang with a street under drive kit on it and it dyno'ed at 1 more hp at the wheels and the lights and ac were dim and i had to upgrade the alternator to 00 gauge wire and buy a $300 210 amp alternator and still had problems with dead batterys all the time. OUR CARS put out 14.40 volts stock AND WITH A UNDER DRIVE set up it will only put out around 12.20-12.40 and thats not enuff to keep every thing happy in the electronics of your cars . PLUS if you think of adding a sound system YOU CAN FORGET THAT IDEA. NOT enuff amps or voltage on demand to support it!!! IMO-DONT DO IT-WASTE OF TIME AND MONEY. THEY are only good on full blow drag or road race cars or off shore power boats were you are WOT 80% of the time.

[sound&security]

theres another thing with them-LX cars run cooling fan so you wont see much of a temp change BUT if your car has a fan clutch set up then it will run hotter in traffic due to the water pump turning slower. ITS bad idea all around to run these things.

[DevssrT]

I would tend to agree Ry. Seems like I remember the Mustang guys complaining about having to change alternators like their underwear (once or twice a year) and then it was water pumps that were a big complaint as well. There was a guy on the SRT8OC complaining about his experience with UD pullies and said he'd never run one on his Charger because he learned his lesson with other cars. Could just be because they were Mustangs...IDK lol.

Hmm...silly curstangs...

[HEMISFEAR]

THE ONLY THING IT HURTS IS THE ALERNATOR not being able to keep up with maintaining THE BATTERYS charge level AND yes ON A MUSTANG OR any ford it burns up the brushes in the alternator. ITS not a good idea to run these on a street car and the lx platform is a big NO-NO unless your ride is a full on track car. the under drive pulleys do just that. They under the alternator and power sterring to free up drag BUT at a cost to the chargeing system. THE lx PLATFORMS HAVE 5 computers runing the car and at a idol the charging system isnt runing fast enuff to keep up with the draw of current used by the tcm/pcm/ecu/abs/hal/ac/lights so your amps and voltage drops and the alternator isnt spining fast enuff to replace the charge that the electronics are sucks dowm off the battery. INTURN you lose electronic throttle responce/low voltage to your coil pac and end up will a weak spark/and the pcm and tcm have trouble in working out the information with weak voltage. THIS is a proven fact. THE ELECTRIC SYSTEM is the heart of the car AND me being a ASE and MECP tech CAN SAY THAT THE MONEY YOU SPEND on a under drive set up isnt worth more than 5 hp on the top end at WOT and the battery you will be going threw and the lost throttle respounce down low and the AC system not blowing as cold isnt worth it. I had a mustang with a street under drive kit on it and it dyno'ed at 1 more hp at the wheels and the lights and ac were dim and i had to upgrade the alternator to 00 gauge wire and buy a $300 210 amp alternator and still had problems with dead batterys all the time. OUR CARS put out 14.40 volts stock AND WITH A UNDER DRIVE set up it will only put out around 12.20-12.40 and thats not enuff to keep every thing happy in the electronics of your cars . PLUS if you think of adding a sound system YOU CAN FORGET THAT IDEA. NOT enuff amps or voltage on demand to support it!!! IMO-DONT DO IT-WASTE OF TIME AND MONEY. THEY are only good on full blow drag or road race cars or off shore power boats were you are WOT 80% of the time.


theres another thing with them-LX cars run cooling fan so you wont see much of a temp change BUT if your car has a fan clutch set up then it will run hotter in traffic due to the water pump turning slower. ITS bad idea all around to run these things.

Thanks man! That DOES make sense to me and really, it should be something I should avoid if these are their true side effects. For 5-8 hp, it's just not worth it to me. I wish I would have seen this last week before I bought one though lol. :tantrum1:

[DevssrT]

^^If you bought one Milan, just sell it..im sure someone would jump on it..

[budoboy]

Hemisfear,

I've had one for 2000 miles or more with the same mods as you and haven't noticed anything. I put it in with the cam, etc. so can't comment on added power or lower ET. I have not heard of anyone with SLP pulley who has had a problem ... yet! If you have modded your car as much as you have obviously you are willing to take some risks. Nothing catastrophic is going to happen with a UD pulley so might as well put it in if you have it already.

[Spitzbergen]

I have had one on my Neon for almost 80,000 miles. Stock altenator and the last battery lasted almost 6 years . I did replace the water pump when I changed the timming belt. Still runs cool and the AC is as cold as day one. I believe it's a 35% reduction.

[HEMISFEAR]

Hemisfear,

I've had one for 2000 miles or more with the same mods as you and haven't noticed anything. I put it in with the cam, etc. so can't comment on added power or lower ET. I have not heard of anyone with SLP pulley who has had a problem ... yet! If you have modded your car as much as you have obviously you are willing to take some risks. Nothing catastrophic is going to happen with a UD pulley so might as well put it in if you have it already.

I thought I bought a hardly used one but the vendor offered the guy a complete refund...now I'm curious if they'd sell it as 'new' lol.


I have had one on my Neon for almost 80,000 miles. Stock altenator and the last battery lasted almost 6 years . I did replace the water pump when I changed the timming belt. Still runs cool and the AC is as cold as day one. I believe it's a 35% reduction.

That's pretty good to hear. Was it regular neon or an SRT4?

[Retro]

I haven't heard of one causing any issues once put on. However, a lot of people don't feel that the cost to performance gain ratio is worth the moolah.

[cheatek]

Milan, I've had underdrive pulleys on my Mustang for as long as I can remember, it was one of the first mods I ever did and I can say it definitely made a difference I could feel. The motor spun quicker and had more power (obviously, as it was not wasting hp turning accessories), it was def a great bang for the buck!

That being said I would NOT do it on any dailey driven street car. A track-only car yes, a 75-25% track car yes, maybe even a 50-50 one but that's pushing it and here's my reason. Underdrive pulleys do exactly that, "under drive" your accessories slowing them down and they don't operate properly ... alt doesn't charge the bat or run the car's electronics correctly, water pump doesn't move enough water, a/c doesn't blow cold, stuff like that. On a track car you don't care and would most likely remove all that anyway but on a street car, and one that's driven daily even more so, you NEED that stuff and want it to work properly. I suppose it would depend on what kind of underdrive pulley kit you have as I know there's ones now that are just crank and ones that are for all the accessories, plus I know with my Mustang I had a choice on what % I wanted to "underdrive" them (as in different pulley sizes).

I never had anything go bad from the pulleys but I did have to replace the bat a few times and alt twice and I noticed the a/c not really working, it was a trade off that I stuck with (at idle the lights would dim and the power windows would hardly roll up, things like that). I would say not to do it especially since our cars rely on electronics much more than my older Mustang but idk, maybe things have changed and they can use underdrive pulleys now without it affecting the accessories too much, I'm only reporting my past experience with my Mustang.

Oh one other thought, I think underdrive pulleys are more beneficial on smaller engines that don't develop as much power as bigger ones, spinning accessories uses up more hp on those than on big engines making it much more noticable. Just my 2 cents.

[HEMISFEAR]

Milan, I've had underdrive pulleys on my Mustang for as long as I can remember, it was one of the first mods I ever did and I can say it definitely made a difference I could feel. The motor spun quicker and had more power (obviously, as it was not wasting hp turning accessories), it was def a great bang for the buck!

That being said I would NOT do it on any dailey driven street car. A track-only car yes, a 75-25% track car yes, maybe even a 50-50 one but that's pushing it and here's my reason. Underdrive pulleys do exactly that, "under drive" your accessories slowing them down and they don't operate properly ... alt doesn't charge the bat or run the car's electronics correctly, water pump doesn't move enough water, a/c doesn't blow cold, stuff like that. On a track car you don't care and would most likely remove all that anyway but on a street car, and one that's driven daily even more so, you NEED that stuff and want it to work properly. I suppose it would depend on what kind of underdrive pulley kit you have as I know there's ones now that are just crank and ones that are for all the accessories, plus I know with my Mustang I had a choice on what % I wanted to "underdrive" them (as in different pulley sizes).

I never had anything go bad from the pulleys but I did have to replace the bat a few times and alt twice and I noticed the a/c not really working, it was a trade off that I stuck with (at idle the lights would dim and the power windows would hardly roll up, things like that). I would say not to do it especially since our cars rely on electronics much more than my older Mustang but idk, maybe things have changed and they can use underdrive pulleys now without it affecting the accessories too much, I'm only reporting my past experience with my Mustang.

Oh one other thought, I think underdrive pulleys are more beneficial on smaller engines that don't develop as much power as bigger ones, spinning accessories uses up more hp on those than on big engines making it much more noticable. Just my 2 cents.

Thanks for the info. I simply don't think enough people have had them on their SRT8's for long enough to make a valid assessment of the long-term effects of the pulley. I spoke to a vendor who also said they don't carry them because they like the ATI balancer (at 13% underdrive vs. 25% for the SLP) better. At the price of the ATI with even less ponies noticed...I've drawn the conclusion this is a wait and see mod. Thanks for all the information fellas.